Hi folks
I‘ve designed a circuit, as shown, with a 5 volt AC input fed into a binary counter and from there into a 555 timer which is configured as missing pulse detector. The incoming feed is from a fuel flow transducer which changes frequency based on fuel flow. This circuit is being used to control a fuel transfer pump and it is imperative that the pump is shut off (by the 555 output going low) if there’s a slow-down of flow rate, or any kind of break in signal.
The system works as intended, in that an incoming frequency of over 90Hz will be enough to keep the 555 output high, whereas a lower frequency will take the 555 output low.
However, if the incoming connection is broken (by unplugging the incoming lead), the 555 output stays high.
How do I get the 555 output to go low if the incoming connection is broken?
View attachment 211674
View attachment 211674
Any input would be great.
Thanks
Edge
I‘ve designed a circuit, as shown, with a 5 volt AC input fed into a binary counter and from there into a 555 timer which is configured as missing pulse detector. The incoming feed is from a fuel flow transducer which changes frequency based on fuel flow. This circuit is being used to control a fuel transfer pump and it is imperative that the pump is shut off (by the 555 output going low) if there’s a slow-down of flow rate, or any kind of break in signal.
The system works as intended, in that an incoming frequency of over 90Hz will be enough to keep the 555 output high, whereas a lower frequency will take the 555 output low.
However, if the incoming connection is broken (by unplugging the incoming lead), the 555 output stays high.
How do I get the 555 output to go low if the incoming connection is broken?
View attachment 211674
View attachment 211674
Any input would be great.
Thanks
Edge